The present invention relates generally to a stackable weight plate and weight stack apparatus employing a plurality of the weight plates for use in a weight lifting exercise machine.
There are two basic types of weight plate used in resistance training. The first type consists of free weights used on barbells and dumbbells, which are usually hand held but which can be loaded on a machine. The second type are generally known as selector weights, which are always attached to exercise machines.
Free weights are one of the earliest forms of weight plates used in resistance training or exercising. They are usually circular in shape, and have a central aperture which allows them to be fitted on a round, bar type handle or machine mounted receiver. They typically come in multiple weight increments, and can be loaded or unloaded by the user in order to increase or decrease the resistance during an exercise. This is dangerous, cumbersome, and requires repeated loading and unloading during the course of an exercise routine. It also requires the exerciser to have a quantity of free weight plates on hand. Often, in a health clubs, the weight plates will be moved from one station to another, and it can be hard to locate a specific plate when needed. U.S. Design Pat. No. 406,183 of Zovich illustrates a typical free weight plate of generally circular shape.
Selector weights are stacked one plate on top of another and are a permanent part of a weight lifting exercise machine. A typical weight stack consists of a series of stacked weight plates each with a central opening, and a selector stem engaging through the central openings of the stacked plates. The selector stem has a series of holes, one for each weight in the stack. The stem is attached to the top plate in the stack and protrudes downwards through the stack, and the top plate is linked via a cable and pulley assembly to one or more exercise stations. Each plate has a transverse opening extending from the front of the stack through to the central opening. A selector pin can be inserted through any selected weight in the stack and into the aligned hole in the selector stem. The selected weight and all weights above it in the stack will then be lifted. The amount of resistance can easily be adjusted by removing the pin and inserting it through a higher or lower weight in the stack, decreasing or increasing the resistance, respectively. The pin therefore selects the number of plates to be lifted.
Weight stacks usually travel up and down on a slide or guide rod system, and are connected to a movable exercise member by means of a linkage system such as a belt and pulley, cable and pulley, pivoting linkage, rigid lever arm, or the like.
The selector weights generally come only in relatively large increments of 5, 10, 15, and 20 lbs, for example. Thus, add-on or incremental weights are often provided to allow the exerciser to adjust the weight stack in smaller increments. Thus, if a person using a weight stack with ten pound increments could not make a ten pound step up in resistance, they could add a five pound add-on or incremental weight on top of the stack to increase the resistance by half a step. Normally, add-on weights are not connected in any way to the machine and must be placed on and off the weight stack by the user. These weights can shift during movement and rub against the weight stack guide rods. This will create friction or drag which can be felt by the user.
Selector weight plates are typically made from steel flat bar or cast iron. Steel plates are cut from flat bar stock into a generally rectangular shape. Cast iron plates are poured from molten iron and are also usually rectangular in shape. In all cases, the rear edge or face of the plate is straight and the side edges are at 90 degrees to the rear face. Weight stacks of rectangular weight plates are described in U.S. Pat. No. 5,374,229 of Sencil, U.S. Pat. No. 5,308,304 of Habing, and U.S. Pat. No. 5,779,601 of Ish, III, for example. Some selector weight plates are provided with locating or nesting devices to keep the weights aligned with one another when stacked. One common nesting device is a button and hole device, in which one or two buttons on the top of one weight plate nest into holes located on the underside of another weight plate. Another nesting arrangement involves interlocking sleeves which engage in the central opening of a weight plate and which have a series of ridges and valleys which mate when one weight plate is placed on top of another. The purpose of such nesting arrangements is to help align the plates as they are stacked, and also to prevent shifting or twisting of one plate relative to another during use.
The problem with the button and hole type of nesting arrangement is that the shape and size of the buttons is such that they do not provide much help in preventing the weights from shifting or twisting from side to side. Because the buttons and holes are in line with the guide rods, any shifting will cause the guide rod holes to rub against the guide rods before the buttons can prevent it. This creates friction and causes the exerciser to feel drag in the exercise movement. Also, since the buttons must be cast or molded into the weights, the weight plates are not uniform in thickness. In a casting process, it is preferable for the molds to be a uniform thickness so that molten material is allowed to flow unobstructed through the mold cavity. Any variation could cause the molten iron not to fill the button-forming recess. A less than perfect pour could cause the buttons and holes not to align.
It is an object of the present invention to provide a new and improved weight plate and weight plate system for an exercise machine.
According to one aspect of the present invention, a stackable weight for an exercise machine weight stack is provided, which comprises a plate having a front edge, a rear edge, and opposite side edges, and an upper face and a lower face, the plate having an aperture extending between the upper and lower face for receiving a weight stack selector stem, the front and rear edges having a matching arcuate curvature with the front edge being convex and the rear edge being concave, and the side edges each having an inwardly angled taper from the front edge to the rear edge.
There are several advantages to the shape of the weight plate. The curvature and inwardly angled side edges allow a series of weight stacks to be more easily grouped in a circular or part-circular fashion for a multi-station exercise machine requiring multiple weight stacks. This will take up less space than multiple rectangular weight stacks. The concave rear edges also provides space at the rear of the weight stack allowing a cable to be routed without requiring any additional space.
According to another aspect of the present invention, a stackable weight is provided which comprises a plate having front and rear edges and opposite side edges, upper and lower faces, and a selector stem aperture extending between the upper and lower faces, the upper face having a raised central rib extending from the front edge to the rear edge and the lower face having a central indent extending from the front edge to the rear edge and of shape and dimensions matching that of the central rib on the upper face, whereby plates can be stacked together with the central indent on the lower face of one plate in mating engagement with the central rib on the upper face of an underlying plate. Preferably, each rib and indent has opposite sides which taper inwardly from the front edge to the rear edge of the plate.
The nesting ridge and indent has many advantages over a conventional button and hole nesting arrangement. The nesting rib or ridge and indent arrangement has greater plate-to-plate contact and occurs over a longer area, which provides much more resistance against side to side shifting of the plates. The tapered side edges of the ridge and indent also prevent the plates from shifting forwards relative to one another. Preferably, the entire center section of the plate is raised to form the opposing rib and indent, so that the overall thickness of the plate remains uniform. This will produce fewer imperfections during casting, where the plate is made from cast iron, and also improves nesting ability. The plate may be of cast iron, steel, or other materials.
Preferably, the rib and indent each have a linear keyway running away from the front edge and bisecting the selector stem aperture. When two plates are nested together, the keyway in the indent of one plate will be aligned with the keyway on the ridge or rib of the underlying plate, allowing a selector pin to be inserted between the two plates along the keyways and through a hole in the selector stem, in order to chose the number of weight plates to be lifted in an exercise.
According to another aspect of the present invention, a weight stack system for an exercise machine is provided, which comprises a plurality of identical weight plates stacked vertically, each plate having an upper face, a lower face, a front edge, and a rear edge, and a central selector stem aperture extending between the upper and lower faces and aligned with the other selector stem apertures in the stacked plates, and a raised central ridge section extending from the front edge to the rear edge to define a raised ridge on one face and a matching indent on the other face, whereby the raised ridge on one plate nests into the indent on an adjacent plate in the stack for nesting and alignment.
Preferably, each ridge and indent have opposite side edges which taper inwardly from the front edge to the rear edge of each plate. The mating ridges and indents thus resist relative side to side movement of the plates, as well as forward shifting of one plate relative to another in the stack.
In a preferred embodiment of the invention, a top plate is provided for placing on top of the stack and securing to the selector stem. The top plate is of similar shape and design to the plates in the remainder of the stack, but is preferably of smaller cross-sectional dimensions and greater thickness than the other weight plates. The top plate has the same raised central ridge as the other plates.
Preferably, a plurality of add-on weights are provided for selective placement on the top weight plate of the stack. Each add-on weight weighs less than the other plates in the stack. Each add-on weight comprises a plate having a front edge, a rear edge, opposite sides, and opposing upper and lower faces. The lower face has an indent for mating engagement with the raised ridge on the upper face of the top plate of the stack. The add-on weight has a through bore extending from the upper face to the lower face for alignment with the selector stem apertures, and a slot extending from one of the front or rear edges to the through bore for allowing the add-on weight plate to be fitted over the weight stack cable when being placed on top of the stack. Preferably, the indent terminates short of the rear edge, preventing the add-on weight from sliding forward and falling off the stack. The indent which fits over the raised ridge on the top plate prevents lateral sliding of the add-on weight. Add-on weights can be stacked on top of one another and locked in place. This allows ready and secure adjustment to provide intermediate weights between the weight stack plate weights.
The weight plate and weight stack system of this invention provide improved and more secure nesting ability, as well as a more aesthetic appearance to the weight stack, and more space conservation where multiple weight stacks must be arranged together.